sticky bit.sh

$ mkdir tmp
$ sudo chown root:root tmp # change owner to root
$ sudo chmod o+w tmp       # add permission to other user to add files
$
$ sudo mkdir tmp/123     # create a directory owned by root
$ sudo chmod 777 tmp/123 # give all permissions, so other user can remove it.
$ rm -r tmp/123          # remove it without any problem.
$ 
$ sudo mkdir tmp/123     # create a directory owned by root again
$ sudo chmod 777 tmp/123 # give all permissions, so other user can remove it.
$ sudo chmod +t tmp      # set on sticky bit
$ rm -r tmp/123/         # try to remove it.
rm: cannot remove `tmp/123': Operation not permitted
$